MAGNETIC-RESONANCE OF FE-S CLUSTERS - ISOLATION AND CHARACTERIZATION OF A 7FE FERREDOXIN FROM RHODOPSEUDOMONAS-PALUSTRIS

A novel iron-sulfur protein from the photosynthetic purple bacterium R hodopseudomonas palustris was purified to homogeneity and identified a s a ferredoxin on the basis of its physicochemical properties. Based o n the uv/vis spectrum, iron quantitation, cyclic voltammetry, EPR, and H-1 NMR data, the ferredoxin is found to contain two iron-sulfur clus ters, one [3Fe-4S] and one [4Fe-4S], which places this protein in the class of 7Fe ferredoxins. The voltammetric peak potentials of the two clusters are -0.260 and -0.560 V at pH 8.0. The molecular mass around 19 kDa makes this protein the heaviest known in this class. This paper further demonstrates the diagnostic power of magnetic resonance spect roscopies in recognition of the two types of clusters in iron-sulfur p roteins. (C) 1995 Academic Press, Inc.